Patch "net/sched: sch_hfsc: Ensure inner classes have fsc curve" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net/sched: sch_hfsc: Ensure inner classes have fsc curve

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-sched-sch_hfsc-ensure-inner-classes-have-fsc-cur.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit fcb9298752943c3056268cfa0a536aa280b29dee
Author: Budimir Markovic <markovicbudimir@xxxxxxxxx>
Date:   Thu Aug 24 01:49:05 2023 -0700

    net/sched: sch_hfsc: Ensure inner classes have fsc curve
    
    [ Upstream commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f ]
    
    HFSC assumes that inner classes have an fsc curve, but it is currently
    possible for classes without an fsc curve to become parents. This leads
    to bugs including a use-after-free.
    
    Don't allow non-root classes without HFSC_FSC to become parents.
    
    Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
    Reported-by: Budimir Markovic <markovicbudimir@xxxxxxxxx>
    Signed-off-by: Budimir Markovic <markovicbudimir@xxxxxxxxx>
    Acked-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230824084905.422-1-markovicbudimir@xxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index b18ec1f6de60c..fa3d2fd4990ce 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1021,6 +1021,10 @@ hfsc_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 		if (parent == NULL)
 			return -ENOENT;
 	}
+	if (!(parent->cl_flags & HFSC_FSC) && parent != &q->root) {
+		NL_SET_ERR_MSG(extack, "Invalid parent - parent class must have FSC");
+		return -EINVAL;
+	}
 
 	if (classid == 0 || TC_H_MAJ(classid ^ sch->handle) != 0)
 		return -EINVAL;